I found this pen at a local antique mall. It appears to be a 1st generation vacumatic standard with longitudinal transparency and a date code of 1936. It is in mint conditioning and still has the original price tag attached. I have a couple of questions which I hope someone can answer. 1) How common are the longitudinal transparency? Did all vacumatic standards have this configuration? 2) Since this is the most expensive pen I have bought, I am curious about its value. 3) The seller attached the price tag with tape which left behind a sticky residue. What is the best way to remove the tape residue? Cheers Billy